A printing plate has a surface which defines an image to be printed. The printing plate is mounted on a rotatable plate cylinder in a printing unit. Ink is applied to the printing plate on the plate cylinder, and the inked image is transferred to paper or other material when the cylinder rotates in the printing unit.
The printing plate is formed as a thin sheet of metal, and is mounted on the plate cylinder by wrapping the sheet around the cylindrical outer surface of the cylinder. When the plate is thus mounted on the cylinder, opposite edge portions of the plate extend axially along the cylinder. A lock-up assembly within the cylinder engages the opposite edge portions of the plate to hold the plate securely on the cylinder when the cylinder rotates.